I would suggest a comma after "dinghy" and another one after "discarded", and that you remove the comma after "succulence". And maybe just call the poem "Midsummer"? Or something else entirely that isn't just a repeat of information the poem itself supplies.

On first read, this poem reminds me of Amy Clampitt -- she often wrote of nature with proper names, terminology I can only describe as rich and polyglottic (which might be synonymous for rich language).

I don't mind the modifier after its object, with regards to the discarded carcass. Although it deviates from how men speak.

I like the short opener of S2 -- it's important to mix in terseness. I think Hugo's Triggering Town overrated, but remembered the lesson well from it about mixing up the length of sentences for aural variability.

It all seems a lovely paean to the beautiful- and ugly-sides of nature. My one criticism was going to be a lack of human presence, but the queen of weeds is there, "Mother Nature." And I suppose the squinting day could be "Father Time."

The rhyming brings to mind Nemo's poem about lines to be left in the ground recently, and I'd done that sort of thing too (in Merrill at bedtime). It's a fun way to make the reader's eye and ear team up. Someone commented on my near lack of human presence in Missouri Rag too. These are the tools of our trade. Hollander might call them meaning-making tools.

Returning from the above tangent, I think this a successful poem, I should add

I am home after long travels, and able to comment. So: to me, S 1 and S 3 are pristine as is, and ready to publish. They do you honor as a poet. S 2 I'm afraid I feel a bit more niggly about. I'm not sure you need that zoom in on the local to achieve the poem's mood and goals. It's a little thing I've been trying to do in my own work, with varying success - cut out the mass of details that weighs the poem down, since I often have a lot of it. There's the great story about Hemingway, that it took him to write The Old Man and the Sea since he knew so much about deep sea fishing he could leave almost all of it out.
I found blackwater in the Supplement to the OED: "A stream stained brown by the peat of the mosses from which it flows." The three other definitions don't seem to fit. Is this what you mean? Of course, in my perfect world, this would be moot, since you'd choose to cut S 2 and make S 1 and S 3 your poem. One that I think is very fine.
I am agnostic about your title.
Oh - I also remember an article about Keats editing his odes. Keats was taking out some fine lines of poetry, which had taken obvious work, because they were tangential to the poem he was building.

Cheers,
John

A footnote to my argument. You've already got cicadas - not sure you need dragonflies at that point.

I really enjoy the vivid imagery of this poem. I am transported to the pier at once. It reminded me of The Shampoo by Elizabeth Bishop.

This is a slight reservation that I am not sure about myself. Lapped used as a participle in ‘beside the lapped pier’ gave me pause. The participle form typically indicates some continuous condition or other rather than a single action or series of actions—think the passed field versus passing the field. Seeing as waves lapping the pier is a series of actions, lapped seemed oddly at odds with the way waves interact with the pier. Also, in case it matters, we do not say what by? I would expect something like a wave-lapped pier. Again, I am not sure, though, if either one or both of those potential concerns rise to the level worth changes, but I suppose that is for you to decide anyway.

I reckon your syntax is aptly adjusted to accommodate the sense of the quiet and still moment in time that you paint, such as in ‘Bubbles on blackwater.’ The lack of verb smacks of stasis and things just being, if you will. I especially appreciate the description of the sunrays and ‘the long-armed queen of weeds’ that surprised me at the end. No more nits from me. Well done!

For “meridian,” Ann, I went back and forth about that word choice. I ended up choosing “meridian” because it’s more the norm in the U.S. (I think). I agree though that “meridiem” is richer. But now it’s a moot point because I’ve shortened the title.

Roger, good suggestions: I’ve added the commas in S1 and shortened the title. A short quiet poem now has a quiet title. I like the simplicity of it. The one thing I didn’t follow was removing the comma after “succulence,” since that would change the meaning (while having it shows that the queen of weeds is that succulence). But maybe you’re better at commas than I am, so if you have something specific in mind do let me know.

Jake, I’m glad you enjoyed the rhyming, also a favorite part for me. Interesting the Amy Clampitt observation, I’ll have to pull my Collected of hers off the shelf and read a poem or two. The human presence part, yeah, I wondered about that myself, but then found I liked the lack of it for heightening the solitude of the scene.

John, thanks for your thoughts. I have been playing with your interesting suggestion about cutting S2, but I’m not coming down there, yet anyway. I like the pause there, the zoom focus moment before the epiphanic stuff in S3. The sensualness of the details slows things down to increase the sense of stillness. Also, there’s a parallel between the carapaces and the dinghy-carcass in S1 which I feel has some symbolic resonance. For “blackwater” I simply meant “black water,” but enjoyed writing it as a compound, which made it feel blacker, especially after “bobs” and “bubbles.” I’m happy you like this poem.

Eric, I was just about to post this when I read your comment. Thank you, I’m glad you enjoyed it. I’m going to keep “lapped” in part for the unexpectedness of it—where “wave-lapped” is implied. Also, the double stress is onomatopoeic for the waves’ hitting the pier, which makes it more palpable. And that Bishop poem—what a beauty! I will be by a lake today and I might just bring EB along with me.

I'm on the fence about S2. One thing I don't like is the break here...

dragonflies' egg
deposits

The apostrophe, though technically correct reads a little preciously, especially given the seemingly singular egg which doesn't become the plural egg deposits until the following line. It seems unnecessarily complicated as far as lineation, though echoing that rhythm by separating nymph-stage and carapaces does help me to recover my balance a bit.